Experiment and Simulation of a Selective Subwavelength Filter with a Low Index Contrast

Abstract

Subwavelength gratings have been of great interest recently due to their ability to eliminate multiple orders. However, high index contrast (Δn∼3) is typically achieved using metals or high-index dielectrics surrounded by vacuum in order to maintain good optical selectivity. Here, we theoretically propose and experimentally realize a selective subwavelength grating using an index contrast of Δn∼1.2 without vacuum. Despite its low index contrast, our simulation and experiments show that good optical selectivity is achieved using the same physics as subwavelength gratings made of high-index contrast. Such polymer-based encapsulated gratings are easier to scale up for use in large-area applications such as photovoltaics and lighting.

Wavelength influence on the determination of subwavelength grating parameters by using optical scatterometry

“…2 is computed up to 1300 nm above the surface of the same silicon-on-silicon grating. As mentioned in a prior research, the reflectivity of the grating containing silicon layers is dependent on the angle of incidence [22,23]. Therefore, shining the light at different incident angles in subwavelength regime might affect the near field sensitivity to the change of grating parameters.…”